HRM's with "fat burn" function


New Member
I've never had any real faith in the accuracy of the "Calories used" or "Fat burn" functions of Heart Rate Monitors (HRM's). Afaik it isn't possible to derive such data with any real accuracy from the data available to these devices (mine is also a "regular" computer, so it also has speed data). Having said that, I do look at the figure after each ride, not for the absolute value it displays, but to get a relative indication. Even though I don't believe the value it displays, it does provide me with a bit of motivation and sense of accomplishment.

But my computer/HRM shows strange results for different rides, for my regular 90KM ride which includes ~1400M climbing it indicates 0.3KG fat burned, this strikes me as a plausible figure. The strange thing is that it can show much higher figures for shorter rides with little or no climbing, for the 80KM ride I did today with ~700M climbing it indicated 0.9KG fat burn. That figure strikes me as much too high an estimate. The manual that came with mine doesn't explain how it calculates these figures, I was wondering if other makes of HRM's explain how they calculate the figure.

It is believed that the body preferentially burns fat in the training zone where the heart rate lies between 60% and 70% [1]. So I wonder if HRM's take that into account. This could explain the results I get. My regular 90KM ride (0.3KG fat burn) requires me to work harder than the ride I did today (0.9KG fat burn).

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